‘Green light’ lies
A ‘charge completed’ light does not necessarily mean a battery is at its capacity-or in a good state of health. When a battery is charging, the ready light will eventually illuminate, indicating that the battery is fully charged. The user assumes that the battery has reached its full potential and the battery is taken in confidence.
The green light does not actually guarantee sufficient battery capacity or ensure state-of-health. Similar to a toaster that pops up the bread when brown, the charger fills the battery with energy and “pops” it to ready when full. Charge termination is commonly detected by a rise in battery temperature.
The rechargeable battery is a corrosive device that gradually loses its ability to hold charge as part of natural aging, as shown in Figure 1 on page 38. Many users are oblivious to the fact that their batteries barely last a day, with no reserve energy to spare. In fact, weak batteries can hide comfortably because little demand is placed on them on a routine day. The situation changes when full performance is required during an emergency. Total collapse of portable systems is common, and such breakdowns are frequently related to poor battery performance.
Carrying larger batteries or switching to higher energy-dense systems does not ensure better reliability if the weak batteries are not “weeded” out. Likewise, the benefit of using advanced ultra-high capacity systems offers little advantage if the packs are allowed to dwell in the fleet once their performance has dropped below an acceptable level.
Figure 2 on page 39 illustrates four batteries with different ratings and state-of-health conditions. Batteries B, C and D show reduced charge acceptance because of memory problems and other deficiencies. The worst pack is battery D; it switches to ready after only 14 minutes of charge (assumed time). This battery is a likely candidate to be picked when a fresh battery is required in a hurry. Unfortunately, this pack will last only for a brief moment. Battery A, on the other hand, has the highest capacity and takes the longest to charge. Ironically, battery A is least likely to be picked because it is slowest to charge.
The weak batteries are charged quicker and remain on “ready” longer than the good batteries. The bad batteries tend to gravitate to the top, making them available for the unsuspecting user. In an emergency situation that requires quick charge action, the batteries that are on ready may be “deadwood.”
Maintenance and quality control The reliability of portable equipment is based on the integrity of the battery. While most equipment receives scheduled maintenance and calibration, batteries get little support. Historically, batteries are serviced either when they no longer hold charge or when the equipment is sent in for repair. As a result, battery-operated devices become unreliable with time. Implementing a battery maintenance plan demands effort and commitment on behalf of management. Battery maintenance must become an integral component of an organization’s overall maintenance and repair activities.
Whether the batteries are maintained in-house with their own battery analyzers, or sent to an independent firm specializing in that service, sufficient spare batteries must be kept on hand to replace those temporarily taken away from service. Never indiscriminately remove batteries without ensuring proper replacement.
After service, the batteries are marked to identify performance and service dates. This is best done by attaching a battery label. With the basic battery information shown on the label, a user removing a battery from the charger will look for a good capacity reading and current date.
Battery analyzers are now available that automatically print a label with individual battery ID number, date, name of organization and capacity when the battery is removed from the unit. A sample of such a label is illustrated in the inset on page 40.
Battery maintenance made simple Several methods are available to maintain a fleet of batteries. Only 30 minutes per day should be required for a technician to maintain the system. The equipment needed is at least one battery analyzer capable of producing battery labels.
When taking a battery from the charger, the user checks the service date on the battery label. If expired, the battery is placed into the box marked “To be serviced.” Periodically, the box is removed and the batteries are serviced and re-certified with a battery analyzer.
Battery maintenance has been simplified with the introduction of battery analyzers that offer target capacity selection. This feature works on the basis that all batteries must meet a user-defined performance test or target capacity. Nickel-based batteries that fall short of the required capacity are automatically restored with the analyzer’s recondition cycle. (See Figure 3 on page 40.) Batteries that fail to recover are subsequently replaced with new packs.
In reconditioning, the battery is first discharged to 1V per cell, after which the discharge continues at a much reduced current. While removing the remaining energy from the battery, the molecular structure of the cell is reset to its original chemical composition, and the cell is rebuilt. This process commonly restores nickel-based batteries to full service.
It should be mentioned, however, that batteries with high self-discharge and those containing shorted cells cannot be corrected with recondition; neither can a battery that is worn out because of old age or one that has been damaged through abuse.
A practical target capacity setting for most battery applications is 80%. Increasing the capacity to 90% will, in essence, raise the performance level by 10 points. It should be noted that higher settings will yield fewer batteries because older batteries often cannot reach 90% capacity.
The target capacity setting of a battery analyzer can be compared to a student entry exam for college. With a passing mark of 80%, a reasonable number of students will pass. If the passing mark is set to 90%, fewer but better-qualified students will be admitted.
After service, the batteries are re-labeled and returned to the charger. Those batteries that fail to meet the target capacity are replaced with new packs. All batteries in the charger are now certified to meet a required performance standard.
Public safety applications Organizations tend to postpone battery maintenance until a crisis situation develops. A fire brigade using portable radios had chronic communication problems, especially during calls lasting longer than two hours. The symptom manifested itself in their radios not transmitting, although reception worked fine. This situation left the firefighters in an awkward position because they were unaware that their call did not get out.
The fire brigade acquired a new battery analyzer and all batteries were serviced through exercise and recondition methods to restore lost capacity. Those batteries that did not recover to a preset target capacity were replaced. Shortly thereafter, the fire brigade was summoned to a 10-hour call that demanded heavy radio traffic. To their astonishment, none of the portable radios failed. The success of this flawless operation was credited to the excellent performance of their batteries.
Emergency preparedness Batteries placed on prolonged standby commonly fail when put to the test. Such was the case when one of our representatives was allowed to tour a state emergency management facility in a large U.S. city. In the fortified underground bunker, more than 1,000 batteries were kept in chargers. The green lights glowed, indicating that the batteries where ready at a moment’s notice. The officer in charge stood erect and in an assured voice said “We are prepared for any emergency.”
The salesman then asked the officer for a random battery from the charger to check its state-of-health. Within seconds, the battery analyzer detected a fail condition. In an effort to make good, the officer handed another battery from the charger bank, only to find out that it also failed. A third battery that was selected failed, too.
Scenarios such as these are quite common. The disturbing fact is that little is done to correct the flaw in the system, once discovered. Commonly, extra funding is not available at that time. All the officer can do is pray that no emergency will occur.
Military applications Another user group that relies heavily on batteries is the military. Defense organizations take pride in using the highest quality and best-performing equipment. When it comes to batteries, however, there is an apparent lack of discipline, and maintenance is frequently ignored. The battery often escapes the scrutiny of a full military inspection, and only the visual appearance is checked. Little effort is made in keeping track of the battery’s state-of-health, cycle count and age. Eventually, weak batteries get mixed in with the new ones and the system becomes unreliable. In some cases, the batteries soldiers carry might as well be rocks.
Choosing an analyzer Today’s market offers a wide selection of battery analyzers at various prices. Two basic types of systems are available: fixed current and programmable units. While fixed current units are usually less expensive, programmable units are more accurate, easier to adapt to different battery types and more effective in restoring weak batteries. The results are higher battery recovery, reduced operator time, increased throughput, simpler operation and the use of fewer trained technicians.
An advanced battery analyzer, such as the Cadex C7000, shown in the photo on page 37, evaluates the condition of each battery and implements the appropriate service to restore battery performance. A recondition cycle is applied if a user-selected capacity level cannot be reached.
The battery settings are stored in interchangeable battery adapters that configure the analyzer to the correct function when installed. Service programs address the different battery needs and include: “ohm test” to measure the battery’s internal resistance; “prime” to prepare a new battery for field use and “auto” to recondition a weak battery when the need arises. In addition, custom programs allow the user to create specialized programs such as self-discharge test and life cycling.
Analyzers capable of printing service reports and battery labels simplify battery maintenance and help in the scheduling of battery service. To manage a large battery fleet, battery analyzers should be capable of interfacing to PC software that simplifies battery maintenance. The user just enters the battery model number and the software automatically sets the correct parameters in the analyzer. Battery manufacturer, vendor references, price, purchase date and performance history of all batteries are stored in a database and are made available for cost analysis and performance verifications.
A battery maintenance system should be automated to demand minimal time. The operator’s task should consist of nothing more than scheduling, replacing and marking the batteries serviced. Occasional selecting of correct current rating and chemistry may also be necessary.
Properly used, a battery maintenance system should generate major cost savings in terms of reduced battery purchases and more dependable service. The payback of a battery maintenance system is known to be one year or less. Enthusiastic users of advanced battery analyzers have reported payback periods of only a few months after batteries that were classified as dead have been restored to full service.